Need to add a default value to a returned SQL SELECT queried list

Question

We have a Kentico 13 page type field with a Drop-down list form control that queries a db table to populate the list.

Currently, the list pre-selects the top value, but this won't work because it's not a required field, so I'm wondering if there's a way to add a default "Select one" value to the dropdown list.

Things to note:

• To be clear, I don't need to add a default value to the table.
• I also have no further control over this dropdown list, so the default has to be added in the SQL query itself.

Below, is the original query that returns the appropriate list. The only thing that's missing is a default value.

SELECT t.NodeGUID, t.DocumentName FROM VIEW_CMS_TREE_JOINED t WHERE t.ClassName = 'AscediaRedesign.Industry' ORDER BY t.DocumentName

Below is a screenshot of how we set up the page type field (using the above SQL query), followed by another screenshot of the successfully populated dropdown list:

A member of the Kentico community suggested trying a UNION, but I was unable to get this to work:

SELECT '' as NodeGUID, 'Please Select' as DocumentName UNION SELECT t.NodeGuid, t.DocumentName FROM VIEW_CMS_TREE_JOINED t WHERE t.ClassName = 'AscediaRedesign.Industry'

The above query results in this error: "Caused exception: Conversion failed when converting from a character string to uniqueidentifier."

Answer 1

Try below queries. Blank is not valid GUID. That is the reason for the error.

SELECT NEWID() as NodeGUID, 
       'Please Select' as DocumentName 
 UNION ALL 
SELECT t.NodeGuid, 
       t.DocumentName 
  FROM VIEW_CMS_TREE_JOINED t 
 WHERE t.ClassName = 'AscediaRedesign.Industry' 

or

SELECT NULL as NodeGUID, 
       'Please Select' as DocumentName 
 UNION ALL 
SELECT t.NodeGuid, 
       t.DocumentName 
  FROM VIEW_CMS_TREE_JOINED t 
 WHERE t.ClassName = 'AscediaRedesign.Industry'